As is known, a fuel cell generates electricity by an electrochemical reaction of hydrogen and oxygen. The fuel cell receives a chemical reactant from the outside even without a separate charging process and generates a continuous power.
The fuel cell may be formed by disposing separators (separation plates or bipolar plates) at both sides of a membrane-electrode assembly (MEA) with the membrane-electrode assembly interposed there between. A plurality of fuel cell sheets may be continuously arranged to form a fuel cell stack.
In the membrane-electrode assembly, which is a core component of the fuel cell stack, an anode electrode layer (catalyst layer) is formed on one surface of an electrolyte membrane, and a cathode electrode layer (catalyst layer) is formed on another surface thereof with the electrolyte membrane interposed there between.
Sub gaskets for protecting the electrode layers and the electrolyte membrane and securing an assembly property of the fuel cell are bonded to edge portions of the respective electrode layers of the membrane-electrode assembly. In the meantime, gas diffusion layers (GDL) for diffusing reacted gas of hydrogen and oxygen are integrally bonded to the electrode layers of the membrane-electrode assembly, respectively.
The fuel cell stack components including the membrane-electrode assembly, the sub gaskets, and the gas diffusion layers may be manufactured by integrally bonders of the sub gaskets to the membrane-electrode assembly to which the sub gaskets are bonded (hereinafter, referred to as an “MEA basic material” for convenience), and integrally bonding the gas diffusion layers to the entire surface of the electrode layer.
In general, a method of bonding the gas diffusion layers to the MEA basic material employs, for example, a hot press device for compressing the MEA basic material and the gas diffusion layers at a high temperature and a high pressure in a state where the gas diffusion layers are disposed on both surfaces of the MEA basic material, and integrally bonding the MEA basic material and the gas diffusion layers.
However, in a case where the MEA basic material and the gas diffusion layers are compressed at the high temperature and the high pressure by using the hot press device, moisture of the sub gasket is evaporated by heat applied from the hot press device, and thereby contracting and forming wrinkles on the surface of the sub gasket. The wrinkles on the surface of the sub gasket cause a leakage of reacted gas when the fuel cell stack is manufactured, thereby deteriorating performance of the fuel cell stack.
The membrane-electrode assembly includes a platinum catalyst and an ion conductive polymer film such as Nafion, and the ion conductive polymer film needs sufficient moisture therein in order to secure ion conducting performance.
However, most of the moisture inside the ion conductive polymer film evaporates during the compression process at the high temperature and the high pressure by the hot press device, so that the membrane-electrode assembly loses its inherent ion conducting performance. Accordingly, after the fuel cell stack is manufactured, it is necessary to re-supply sufficient moisture to the ion conductive polymer film through an activation process of the membrane-electrode assembly.
When the activation process of the membrane-electrode assembly is conducted after the fuel cell stack is manufactured, hydrogen and electric energy are rapidly consumed, and as a result, manufacturing cost of the fuel cell stack is increased, and a manufacturing cycle time is unavoidably increased.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.